Satellite broadcast systems have been in operation for many years. In a typical system, an uplink site transmits a radio signal to a satellite which receives the radio signal and then retransmits the radio signal towards Earth. The retransmitted radio signal is received at a downlink site, thereby completing the satellite radio broadcast transmission.
The antennas used at both the uplink and downlink sites utilize very high signal gain and narrow directivity due to the long transmission distances and the relatively low transmission powers involved in such systems. The directivity of these antennas also provide for selectivity between satellites which are operating at or near the same frequency band and which are spaced relatively near one another.
The aforementioned radio signals are typically modulated with information. Audio, video, and data information are commonly transmitted. Often times a given satellite receives and transmits one or more of these three types of information simultaneously.
Satellites are classified by the altitude at which they orbit Earth. Correspondingly, the altitude at which a satellite orbits determines the period of its orbit around Earth. A certain class of satellites, which are stationed at an altitude above earth such that the satellite's period of orbit is equal to the earth's orbital period and which are located at a zenith with respect to a point along the Earth's equator, are called geosynchronous orbit satellites. Or, geosynchronous satellites. Geosynchronous satellites are advantageous because they appear to be stationary from earth and they allow a downlink site with a fixed position antenna to continuously receive radio signals without a need to track any relative movement between the satellite and Earth.
International agreement and United States federal law have provided for the operation of a plurality of geosynchronous satellites which receive and rebroadcast television receive-only (TVRO) signals. These satellites operate in the C and Ku frequency bands. The C-band operates at uplink frequencies in the 6 GHz range and downlink frequencies in the 4 GHz range, the Ku-band operates at uplink frequencies in the 14 GHz frequency range and downlink frequencies in the 12 GHz range. In some types of satellite systems, other frequency bands may be used. End users who operate TVRO downlink sites are enabled to receive TVRO signals.
Each of the C-band and Ku-band TVRO satellites employ several transponders, usually twenty-four in C-band and 32 in Ku-band, that each have a given operational bandwidth, usually 36 MHz. In operation, each of the transponders can be viewed as a separate satellite radio channel. The frequencies of operation of each of the transponders are distinct from others on a given satellite, however, the range of frequencies covered by all the transponders in any given geosynchronous satellite are usually contiguous. In order to improve the isolation of adjacent transponder signals in a given satellite, satellite designers employ the use of orthogonal signal field polarity between transponders that are adjacent in frequency. An arbitrary use of the horizontal and vertical electric signal field polarity descriptors used in terrestrial radio systems is used in satellite systems. Therefore, every-other transponder in most geosynchronous satellites has a vertical electric field polarity and the alternate every-other transponder has a horizontal electric field polarity, the two polarities being orthogonal to one another. This scheme is typically used in C-band satellites and sometimes used in Ku-band satellites. Ku-band satellites do not necessarily alternate between the vertical and horizontal polarities. However, other polarization formats may be used, circular polarization for example.
In a further use of signal isolation through polarity management, separate satellites that are adjacent to one another in orbit are sometimes given opposite polarities with respect to each transponder starting with the first, or the number one, transponder. Thus, if the first transponder in a given satellite has a vertical polarity, then that satellite is said to have a normal polarity. Alternatively, if the first transponder in a given satellite has horizontal polarity, then that satellite is said to have an inverse polarity.
By definition, all geosynchronous satellites orbit directly above the equator and therefore, each satellite's location can be defined by its position in degrees of longitude. Satellites useful for broadcast to the continental United States and other territories are located from about 69 degrees west to 139 degrees west longitude.
As a practical matter, satellites do not stay at a precise location, but rather tend to drift slightly in their relative position with respect to each and the earth. Further, satellites have a finite life span and need to be decommissioned and replaced from time to time. Also, new satellites are occasionally added to the geosynchronous orbit so that total channel capacity can be increased. Also, sometimes a satellite is decommissioned without being replaced. Sometimes, a replacement satellite will have the same characteristics as the satellite it replaces. Other times, the replacement satellite may be located at a different angle of longitude or have the opposite polarity of the satellite it replaced.
In order for a TVRO satellite receiver to properly receive satellite signals, it must have information about the position of the satellite, the polarity of the satellite, and the frequency of operation of the satellite. Further, in order for the selection of satellite signals and programming choices to be convenient and useful to an end user, the satellites are given names and abbreviations so that program guides, user interfaces displays and in other instances, the particular satellites can be identified.
When a TVRO satellite receiver is initially installed at an end user's downlink site, a service technician, who is skilled in things related to satellite downlink sites and receivers, usually installs the equipment and programs a memory in the satellite receiver with the satellite information for the various satellites from which signals are to be received. However, as changes occur in the satellite information for the reasons described above, it is necessary to provide satellite update information to the satellite receiver in order to keep the satellite memory programmed with current satellite information so that the end user can receive all desired satellite radio signals.
The loading of satellite update information into a memory in the satellite receiver poses a problem to the end user. First the end user must make himself aware of the need to add satellite update information, then the user must manually program such satellite update information into the memory of the satellite receiver. Clearly there is a need to streamline and automate the process of maintaining and entering satellite update information into a satellite receiver.